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A-level Chemistry Yr 12 Mine > C14- Alchols > Flashcards

C14- Alchols Flashcards

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1
Q

What does anhydrous mean?

A

Containing no water molecules

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2
Q

What is an elimination reaction?

A

The removal of a molecule from a saturated molecule to make an unsaturated molecule.

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3
Q

What is dehydration?

A

An elimination reaction in which water is removed from a saturated molecule to make an unsaturated molecule.

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4
Q

What does unsaturated mean?

A

Contains a multiple carbon-to-carbon bond.

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5
Q

What does saturated mean?

A

Containing single bonds only.

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6
Q

What are polar molecules?

A

A molecule with an overall dipole, having taken into account any dipoles across bonds and the shape of the molecule.

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7
Q

What is a primary alcohol?

A

An alcohol in which the -OH group is attached to a carbon atom that is attached to a two or three hydrogen atoms.

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8
Q

What is a secondary alcohol?

A

An alcohol in which the -OH group is attached to a carbon atom that is attached to two carbon chains and one hydrogen atoms.

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9
Q

What is a tertiary alcohol?

A

An alcohol in which to -OH group is attached to a carbon atom that is attached to no hydrogen atoms.

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10
Q

What is an substitution reaction?

A

A reaction in which one atom or group of atoms is replaced by another atom or groups of atoms.

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11
Q

Why are alcohols generally polar?

A

Due to the electronegative hydroxyl group which pulls the electrons away fro, the carbon to the Oxygen.

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12
Q

How can hydroxyl group -OH form hydrogen bonds?

A

The oxygen molecule draws electron density away from the hydrogen giving the hydrogen a slightly positive charge. This positive charge can attract lone pairs from a neighbouring oxygen molecule and form hydrogen bonds.

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13
Q

What are the three properties the alcohols have due to the fact that their -OH can form hydrogen bonds?

A
  • Soluble in water
  • increase in the size of the alcohol decreases the solubility of it
  • Low volatility compared with alkanes
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14
Q

Why are (small) alcohols soluble in water?

A

Alcohols and water form hydrogen bonds between the -OH and H2O, this hydrogen bonding allows it to mix freely with water - so it’s soluble.

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15
Q

Why is it when the alcohols increase in size that their solubility in water decreases?

A

In larger alcohols, most of the molecules are non-polar (the carbon chain with hydrogen), so there is less attraction for the H2O molecules as the alcohol increase in size.

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16
Q

Why do alcohols have a low volatility compared with alkanes?

A

Alcohols also form hydrogen bonds with each other. Hydrogen bonding is the strongest type of intermolecular force so they have a low volatility (don’t evaporate easily into a gas).

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17
Q

Explain the combustion (burning) of alcohol?

A

Alcohols burn completely in a plentiful supply of oxygen to produce carbon dioxide and water.

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18
Q

Write the full equation for the combustion of ethanol?

A

C2H5OH (l) + 3 O2 (g) —> 2 CO2 (g) + 3 H2O (l)

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19
Q

What is another way alcohols can by oxidised without combustion?

A

An oxidising agent

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20
Q

What are some examples of oxidising agents used in the oxidation of alcohols?

A

Acidified potassium dichromate - K2Cr2O7
Dilute Sulfuric acid - H2SO4

21
Q

When is an alcohol completely oxidised?

A

When all the C-C and C-H bonds are broken.

Happens in the combustion of alcohol but not with the oxidising agent which mildly oxidise alcohols.

22
Q

If alcohol is oxidised with dichromate what is the equation and what ions are reduced?

A

Cr2O7 2- —> Cr 3+
Orange solution dichromate (VI) ions is reduced to a green solution containing chromium (III) ions.

23
Q

What is Reflux?

A

The continual boiling and condensing of a reaction mixture back to the original container to ensure that the reaction takes place without the contents of the flask boiling dry.

24
Q

What is distillation?

A

Distillation is the process of separating the components or substances from a liquid mixture by using selective boiling e condensation

25
Q

What are primary alcohols oxidised into with an oxidising agent acidified dichromate (V)?

A

Oxidised to aldehydes and then to carboxylic acids.

26
Q

What is an oxidising agent?

A

A reagent that oxidises (takes electrons from) another species.

27
Q

What are tertiary alcohols oxidised into with an oxidising agent acidified dichromate (V)?

A

Tertiary alcohols don’t react with it

28
Q

How can you only oxidise tertiary alcohols?

A

By combustion, burning them with plenty supply of oxygen.

29
Q

What are secondary alcohols oxidised into with an oxidising agent acidified dichromate (V)?

A

The oxidise into ketones only, not possible to further oxidise ketones.

30
Q

Key points for what primary, secondary and tertiary alcohols are oxidised into with an oxidising agent acidified dichromate (V)?

A

Primary - oxidised to aldehydes and then to carboxylic acids
Secondary - oxidised to ketones only
Tertiary - won’t be oxidised

31
Q

What is the formula, suffix (primary) and prefix (secondary for Ketone?

A

. R. Suffix: -one
/. Prefix: oxo-
O=C
\
R

32
Q

What is the formula, suffix (primary) and prefix (secondary for Aldehyde?

A

. R Suffix: -al
/ Prefix: oxo-
O=C
\
H

33
Q

What is the formula, suffix (primary) and prefix (secondary for carboxylic acid?

A

. OH Suffix: -oic acid
/ Prefix: carboxy-
O=C
\
R

34
Q

What is the equation for the oxidation of secondary alcohols with an oxidising agent?

[O] - Oxidising Agent

A

. H R
| \
R — C — OH + [O] —————> C=O + H2O
| Reflux /
R R

35
Q

Write the equation for the oxidation of propan-2-ol to propanone?

A

. H H H H H H H
| | | | Reflux | | |
H— C — C — C — C — H + [O] ———> H — C — C — C — C = H + H2O
| | | | | || | |
H OH H H H O H H

36
Q

What is the general equation for the oxidation of a primary alcohol with an oxidising reagent?

[O] - The oxidising agent

A

. H OH
distil | Reflux |
R-CH2-OH + [O] ————> R-C=O + H2O + [O] ————> R-C=O + H2O

Primary Alcohol Aldehyde Carboxylic Acid

37
Q

Explain why you must distill a primary alcohol when oxidising this alcohol with an oxidising reagent to form an Aldehyde.

A

To ensure the aldehyde is formed instead of the Carboxylic acid, as distilling prevents any further reaction with the oxidising agent to get to the carboxylic acid.

The aldehyde product has a lower boiling point than the alcohol starting material so will distill out of the mixture as soon as it forms, and collected in separate container.

38
Q

Explain why you must reflux a primary alcohol when oxidising this alcohol with an oxidising reagent to form a Carboxylic Acid.

A

Ensures that any aldehyde formed initially in the reaction also undergoes oxidation to carboxylic acid.

39
Q

Explain how you make a primary alcohol to an carboxylic acid?

A

If a primary alcohol is heated strongly under reflux, with an excess of oxidising agent acidified dichromate, a carboxylic acid is formed.

40
Q

Why do you need an excess of oxidising agent acidified dichromate when turning a primary alcohol to a carboxylic acid?

A

Ensures that all of the alcohol is oxidised.

41
Q

Why would you use refluxing?

A

Organic reactions (compounds involving carbon) are slow and are usually flammable and volatile so have low boiling points.
Therefore if you heat them with a Bunsen burner they’ll evaporate or catch fire before they can react.
Reflux means that the liquid continuously boils, evaporates and condenses back to the flask, giving them time to react. And safer as avoids naked flames.

42
Q

How does a dehydration of alcohols take place.

A

An alcohol is heated under reflux in the presence of an acid catalyst such as concentrated sulfuric acid (H2SO4) or concentrated phosphoric acid (H3PO4).

43
Q

What are the products of an dehydration of alcohol reaction?

A

An Alkene and Water.

44
Q

How is the water molecule formed in the dehydration of an alcohol?

A

The OH and any of the Hydrogen attached to the next carbon.

45
Q

Write all the types of products you can get from the dehydration of butan-2-ol with names?
. H H H H
| | | |
H-C-C-C-C-H
| | | |
H OH H H

A

H H
\ /
C=C But-1-ene
/ \
H CH2CH3

. H H
\ /
C=C Z-But-2-ene
/ \
H3C CH3

. H CH3
\ /
C=C E-But-2-ene
/ \
H3C H

46
Q

What happens when an compounds containing halides ions reaction with alcohols?

A

A substitution reaction takes place.
Where the -OH group is replaced by the halide.
And a haloalkane is created.

47
Q

When creating an haloalkane with alcohols and halides what must also be present?

A

An acid, such as sulphuric acid H2SO4. This is so a hydrogen halide is created and not a sodium halide.

48
Q

Write the overall equation for the reaction of propan-2-ol with H2SO4 and NaBr?

A

CH3COHCH3 + NaBr + H2SO4 —> CH3CHBrCH3 + NaHSO4 + H2O

A-level Chemistry Yr 12 Mine (15 decks)

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